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From:   Anatoly Trosinenko <anatoly.trosinenko@gmail.com>
Date:   Sun, 3 Jun 2018 16:46:27 +0300
Message-ID: <CAE5jQCfu4i5OQbgE-szs8bGzYoTg2VfOeKKh8+R8yKEfxww=6Q@mail.gmail.com>
Subject: Re: PROBLEM: [kernel BUG at fs/fat/inode.c:162] when writing to a
 broken VFAT
To:     OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc:     akpm@linux-foundation.org, linux-kernel@vger.kernel.org
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Thank you, it works!

=D1=81=D0=B1, 2 =D0=B8=D1=8E=D0=BD. 2018 =D0=B3. =D0=B2 14:19, OGAWA Hirofu=
mi <hirofumi@mail.parknet.co.jp>:
>
> Anatoly Trosinenko <anatoly.trosinenko@gmail.com> writes:
>
> > Description:
> >
> > Writing to some file on a broken VFAT partition causes kernel bug
>
> Thanks. This patch should fix this issue.
> --
> OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
>
>
> [PATCH] fat: Use fat_fs_error() instead of BUG_ON() in __fat_get_block()
>
> If file size and FAT cluster chain is not matched (corrupted image),
> we can hit BUG_ON(!phys) in __fat_get_block().
>
> So, use fat_fs_error() instead.
>
> Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
> ---
>
>  fs/fat/inode.c |    7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff -puN fs/fat/inode.c~vfat-dont-bugon fs/fat/inode.c
> --- linux/fs/fat/inode.c~vfat-dont-bugon        2018-06-02 20:15:04.44192=
0069 +0900
> +++ linux-hirofumi/fs/fat/inode.c       2018-06-02 20:15:04.442920067 +09=
00
> @@ -158,8 +158,13 @@ static inline int __fat_get_block(struct
>         err =3D fat_bmap(inode, iblock, &phys, &mapped_blocks, create, fa=
lse);
>         if (err)
>                 return err;
> +       if (!phys) {
> +               fat_fs_error(sb,
> +                            "invalid FAT chain (i_pos %lld, last_block %=
ld)",
> +                            MSDOS_I(inode)->i_pos, last_block);
> +               return -EIO;
> +       }
>
> -       BUG_ON(!phys);
>         BUG_ON(*max_blocks !=3D mapped_blocks);
>         set_buffer_new(bh_result);
>         map_bh(bh_result, sb, phys);
> _

--=20
Anatoly